The means used to date for securing of the aforesaid blades have involved the use of rules provided with pressure screws placed inside the grooves of the cylinders and compressed between the walls thereof. Securement of the blades by said method was always unsafe and lacking in precision, easily displaced during operation and, therefore, of scant utility and poor performance, as the mechanism had to be adjusted constantly.
Other means used have recourse to the coming together of two rules with complementary inclined planes which slide in relation to each other, and flat opposing planes for support against the walls of the grooves, with interposition of the blades, which rest to the lower side on lips provided for the purpose on said rules, which are provided with depth-graduation screws inside the grooves of the cylinders. An example of such devices is shown in U.S. Pat. No. 4,920,843. In this case, the fixing is safe, but the use of special tools is required for the unlocking and attachment of the assembly, this being mechanically complex to embody and, therefore, expensive.
These embodiments therefore suffer from two essential disadvantages: some are extremely simple and unsafe, while others are mechanically complex and expensive.